161
FXUS65 KBOU 120552
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1152 PM MDT Tue Aug 11 2026

.KEY MESSAGES...

- Hot with scattered gusty showers this afternoon and evening. A
  few gusts up to 40-45 mph possible.

- Monsoon moisture arrives Wednesday and lasts through the
  weekend, bringing scattered showers and thunderstorms most days.
  Locally heavy rainfall possible. The best chance of rain across
  the I-25 corridor is Thursday/Friday.

- Cooler temperatures arrive by Thursday and Friday, with a slow
  warming trend by next week.

&&

.DISCUSSION /Through Tuesday/...
Issued at 116 PM MDT Tue Aug 11 2026

The center of a weakening upper level ridge sits near the CO/NM
border this afternoon. Water vapor satellite shows modest amounts
of moisture rotating around the western/northern edge of the
ridge. That`s led to the development of a few showers and a couple
of thunderstorms - mainly across Park County so far. Despite the
increase in mid-level moisture, we don`t expect much more than
some gusty showers across the plains where deep mixing and
inverted-V profiles are still noted on ACARS soundings today.
Expect a fairly similar story to yesterday for the Denver metro,
with a couple of showers and gusty outflow winds, with little in
the way of meaningful rainfall.

The ridge is expected to continue weakening as it pushes off to
the southeast on Wednesday and Thursday, with broad south-
southwesterly flow allowing monsoonal moisture to finally make
it`s long-awaited return. This moisture may be a tad late to
arrive for most of the lower elevations tomorrow, but we should
see good coverage of storms across the higher elevations, with
chances diminishing quickly from west to east across the urban
corridor. Some guidance hints at a weak MCV-like feature
developing tomorrow evening that would at least encourage a few
more storms across the lower elevations... but will be worth
watching to see if that feature persists among the 00z HREF
members. There is also a somewhat conditional slight risk of
severe weather per SPC across the northeastern plains for the
afternoon and evening hours if convection manages to develop.

Thursday appears to have most of the ingredients in place for
scattered to widespread rainfall across most of the foothills and
adjacent plains. A weak surface cold front is expected to push
through late Wednesday night or Thursday morning, with cooling
mid-level temperatures as well. Forecast highs are only in the
upper 70s to low 80s, with dew points increasing to 55-60F. Most
model soundings show sufficient instability, minimal capping, and
continued upslope through the day, along with some sort of weak
mid-level shortwave tracking through the area during the
afternoon. As previous AFDs have noted, forecast soundings largely
support heavy rainfall across the area with precipitable water
increasing to ~1.25", modestly deep warm cloud layers, and
relatively weak cloud layer mean wind. This is not all that unlike
some of the environments we saw in late July, but the subtle
synoptic forcing at least leads to a little more optimism with
this setup.

The overall pattern does not change significantly for Friday.
Continued easterly surface flow will allow for dew points to
remain fairly constant, with slow moisture advection into the
region. Another weak shortwave will encourage another round of
widespread showers and storms across the higher elevations,
spreading east into the I-25 corridor and plains Friday
afternoon/evening.

Precipitation chances will stick around through the weekend with
above normal moisture remaining over the area. The broad ridge
across the southern CONUS is expected to slowly strengthen and
shift back towards the west, which will eventually start to cut
off our moisture feed. In the meantime another weak front or two
could promote additional chances for showers/storms on Saturday,
with higher PoPs sinking south of our CWA by Sunday.

The ridge will make an attempt to build back across our forecast
area early next week, leading to zonal flow redeveloping across
most of the state. That should limit storm chances for a couple of
days (Monday/Tuesday) with temperatures also warming back up
closer to 90F. Looking beyond the forecast period... most ECMWF
ensemble members push the ridge back into a more favorable
position for monsoon moisture to work back into the region, with
broad support from the GEFS and CMCE.

&&

.AVIATION /06Z TAFS through 06Z Thursday/...
Issued at 1152 PM MDT Tue Aug 11 2026

Southwest winds will continue overnight and into Wednesday
morning. Around 14-15Z, winds become lightas they transition to
the north. A Denver cyclone may form after 18Z. Those models that
show the cyclone keep it just east or southeast of DEN, so north
winds are expected through 21Z. After this, outflow from showers
and thunderstorms is expected to bring a wind shift. Most likely a
west or northwest shift, but this will depend on where the
showers/storms form. Airmass this afternoon starts off dry with
limited instability, similar to the past few days, but it will
moisten through the late afternoon and early evening hours.Found
it difficult to decide between PROB30 versus Tempo, and SH versus
TS. It looks to start off like the past few days with high-based
showers and gusty winds, but with much better coverage over the
higher terrain. At 21Z, opted for a westerly outflow wind with a
30 percent chance for thunderstorms (best chance will be along the
DCVZ). Then as the airmass moistens, begin a tempo for TS at
23Z.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

DISCUSSION...Hiris
AVIATION...BM